Technical Field
The present disclosure is directed to coated ropes or belts such as those used in elevator systems, more particularly to coated ropes or belts such as those used to suspend and/or drive an elevator car and/or counterweight of an elevator system, and even more particularly to the load-bearing cords used in such coated ropes or belts.
Description of the Related Art
Traction elevator systems are widely used. In general, a traction elevator system can include a car, a counterweight, one or more coated ropes or belts interconnecting the car and counterweight, a traction sheave to move the coated rope or belt, and a motor-driven machine to rotate the traction sheave. The sheave is formed from cast iron. In some elevators, the coated rope or belt is a rope formed from twisted steel wires. In other elevators, the coated rope or belt is an elevator coated rope or belt with the twisted wires within an outer jacket.
In general, conventional elevator coated ropes or belts can include a plurality of steel wires of specific number, size and geometry for purposes of strength, proper coated rope or belt diameter, cost of production, and/or durability. For example, for a given steel strength, the total cross-sectional area of the steel wires used in the coated rope or belt generally determines the strength of the coated rope or belt. For coated ropes or belts of the same strength, i.e. same total cross sectional area of the steel wires, using more wires (of relatively smaller diameters) would generally increase the cost of production of the coated rope or belt but provide longer fatigue life. On the other hand, using fewer wires (of relatively larger diameters) would generally lower the cost of production of the coated rope or belt but shorten fatigue life, thereby affecting the durability of the coated rope or belt.
In some elevator systems, the coated rope or belt can include several strands, each including filaments, twisted together to form a second-order helical structure with increased strength. Alternatively, the coated rope or belt could include a layer of filaments twisted around a center strand of twisted filaments, such as in a (1+6+12) arrangement. However, those approaches involve multiple winding (twisting) steps, which may require capital hardware and increase production cost and time.
Moreover, conventional cord configurations discussed above include helical filaments with non-uniform spatial orientations, such as different pitch, direction, and/or helical axis. Such non-uniformity may adversely affect the durability of the cord. Moreover, cord of conventional configurations may also generate noise due to such traction tension.
Tension cords are also used in other technology fields. For example, tension cords are used in automobiles to raise and lower windows. However, those cords are formed with filaments that are both micro-sized and made from synthetic resin. Due to the significant difference in dimension, material, and application, filament arrangement in those tension cords are generally considered unsuitable for use in traction elevators